U.S. patent application number 12/731662 was filed with the patent office on 2011-06-09 for apparatus and method for inspecting substrate internal defects.
This patent application is currently assigned to Delta Electronics, Inc.. Invention is credited to Jen-Ming CHANG, Cheng-Kai Chen, Yen-Chun Chou, Yu-Hsi Lee, Jui-Yu Lin.
Application Number | 20110135188 12/731662 |
Document ID | / |
Family ID | 44082066 |
Filed Date | 2011-06-09 |
United States Patent
Application |
20110135188 |
Kind Code |
A1 |
CHANG; Jen-Ming ; et
al. |
June 9, 2011 |
APPARATUS AND METHOD FOR INSPECTING SUBSTRATE INTERNAL DEFECTS
Abstract
A method for inspecting substrate internal defects is disclosed.
The method provides at least one light source disposed on a lateral
side of a substrate and configured to emit a light beam to the
lateral side for correspondingly penetrating the substrate. The
method also provides an image capturing module for retrieving an
image of the upper surface, wherein an incident angle of the light
beam to the respective lateral side is limited within a first
predetermined angle to allow the light beam to have a total
reflection in the substrate. Thus, the light beam is blocked by
internal defects when transmitting within the substrate to generate
bright spots to be detected by the image capturing module for
locating the defect position. The method provides a better image
definition of internal defects images. The present invention
further provides an apparatus based on the method for inspecting
substrate internal defects.
Inventors: |
CHANG; Jen-Ming; (Taoyuan
County, TW) ; Lee; Yu-Hsi; (Taoyuan County, TW)
; Chou; Yen-Chun; (Taoyuan County, TW) ; Chen;
Cheng-Kai; (Taoyuan County, TW) ; Lin; Jui-Yu;
(Taoyuan County, TW) |
Assignee: |
Delta Electronics, Inc.
|
Family ID: |
44082066 |
Appl. No.: |
12/731662 |
Filed: |
March 25, 2010 |
Current U.S.
Class: |
382/149 |
Current CPC
Class: |
G01N 21/9505
20130101 |
Class at
Publication: |
382/149 |
International
Class: |
G06K 9/00 20060101
G06K009/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 4, 2009 |
TW |
098141511 |
Jan 8, 2010 |
TW |
099100393 |
Claims
1. A method for inspecting substrate internal defects, the
substrate has an upper surface and a plurality of lateral sides
connected to the upper surface, the method comprising: providing at
least one light source disposed on one of the lateral sides on the
substrate and configured to emit a light beam to the lateral side
for correspondingly penetrating the substrate; and providing an
image capturing module disposed above the substrate for retrieving
an image of the upper surface; wherein, an incident angle of the
light beam to the respective lateral side is limited within a first
predetermined angle to allow the light beam to have total
reflection in the substrate.
2. The method for inspecting substrate internal defects of claim 1,
wherein the light beam emitted to the lateral side is parallel
light.
3. The method for inspecting substrate internal defects of claim 1,
wherein the incident angle of the light beam to the respective
lateral side is limited within a second predetermined angle, the
second predetermined angle is the far half of the first
predetermined angle away from the image capturing module.
4. The method for inspecting substrate internal defects of claim 1,
wherein the method comprises a plurality of light sources emitting
light beam to the plurality of lateral side respectively for
penetrating the substrate.
5. An apparatus for inspecting substrate internal defects, the
substrate has an upper surface and a plurality of lateral sides
connected to the upper surface, the apparatus comprising: at least
one light source disposed on one of the lateral sides of the
substrate and configured to emit a light beam to the lateral side
for correspondingly penetrating the substrate; and an image
capturing module disposed above the substrate for retrieving an
image of the upper surface; wherein, an incident angle of the light
beam to the respective lateral side is limited within a first
predetermined angle to allow the light beam to have a total
reflection in the substrate.
6. The apparatus for inspecting substrate internal defects of claim
5, wherein the light beam emitted to the lateral side is parallel
light.
7. The apparatus for inspecting substrate internal defects of claim
5, wherein the incident angle of the light beam to the respective
lateral side is limited within a second predetermined angle, the
second predetermined angle is the far half of the first
predetermined angle away from the image capturing module.
8. The apparatus for inspecting substrate internal defects of claim
5, wherein the apparatus comprises a plurality of light sources
emitting light beam to the plurality of lateral side respectively
for penetrating the substrate.
9. The apparatus for inspecting substrate internal defects of claim
5, wherein the plurality of light sources are linear light source
and parallel to the plurality of lateral sides respectively.
10. The apparatus for inspecting substrate internal defects of
claim 5, wherein the width of the light source is larger than the
width of the lateral side.
11. The apparatus for inspecting substrate internal defects of
claim 5, further comprising a carrier for carrying the substrate,
the carrier comprising a base and a transmission module disposed on
the base, the transmission module driving the substrate to move
along a horizontal direction relative to the image capturing
module.
12. The apparatus for inspecting substrate internal defects of
claim 11, wherein the light beam is focused on part of the lateral
side by a condensing lens.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The invention generally relates to an apparatus and a method
for inspecting substrate internal defects.
[0003] 2. Description of Prior Art
[0004] Semiconductor manufacturing processes such as thin film
deposition are used for fabricating electronic components on a
substrate. Accordingly, the quantity of internal defects in the
substrate such as inclusions, bubbles, cracks is a critical factor
indicating the quality of electronic components. In addition,
cracks crack are generated on substrates because substrates undergo
processes such as high temperature heating process and etching and
are transported frequently in manufacturing processes.
[0005] Thus, inspecting internal defects on a substrate is an
indispensable non destructive inspection. At present, the most
frequently used crack inspection method arranges illuminating light
sources beneath the substrate to emit light beam towards the lower
surface of the substrate and penetrate the substrate, and uses a
camera to obtain an image of the upper surface of the substrate
above the substrate. The penetration rate of the light beam is
reduced as the emitted light beam is reflected, refracted and
scattered by internal defects. The image brightness of locations
having internal defects is significantly lowered than other areas
so that the locations and sizes of the internal defects can be
identified by image analysis of human or computing devices
subsequently.
[0006] The image definition of internal defects images determines
the effectiveness of the inspection and efficiency of image
analysis. Therefore, acquiring precise and clear images of internal
defects has been an eager need to resolve in the inspection
processes. Nonetheless, the above internal defects inspection has
the following disadvantages. Firstly, as shown in the schematic
diagram illustrating the above method for inspecting internal
defects in FIG. 1, not only surface pollutants 11 adhered on two
sides of a substrate 10 or the texture of the substrate 10 but also
internal defects 12 such as inclusions or cracks would influence
penetration rate of light beam during the manufacturing process. It
is not effective to differentiate between internal defects 12 and
surface pollutants 11 according to dark spots when interpreting
images retrieved by a camera 30. Frequently, surface pollutants 11
are misinterpreted as internal defects 12.
[0007] As shown in FIG. 2, light beam diffracts as the light beam
is interfered such that micro internal defects 12 in an image may
be faded when emitting brightness of light beam become stronger. In
other words, the image width of internal defects 12 is in inverse
proportion to the light intensity. There are circumstances emitting
light intensity is increased on a thicker substrate 10 in order to
increase image brightness. Yet, when light intensity is higher than
a certain level, light intensity of diffraction generated then
becomes too strong which lowers the image definition of internal
defects 12. Thus, it is required to spend higher cost on a camera
with higher definition to retrieve clear image. In addition, under
the circumstance when the tolerance of a substrate 10 is large, an
optimal light intensity for retrieving the best image becomes a
difficult decision. Further, as shown in FIG. 3, when crack width
of micro defects 12 under non parallel light becomes smaller, it is
difficult to enhance image definition of micro crack by projecting
light from different directions. Photo of the attachment 1 is a
photo of crack image taken by prior art method for inspecting
defects.
SUMMARY OF THE INVENTION
[0008] As a result, the present invention provides an illuminating
method special designed for substrate inspection to resolve the
above problems. The present invention uses the total reflection of
light beam within a substrate to directly illuminate internal
defects in the substrate so as to enhance the image definition of
internal defects such as cracks, pores, impurities, bubbles,
thickness difference and effectively avoid misidentifying foreign
objects such as surface stains as internal defects. In addition to
offering a more efficient capability to inspect internal defect,
the method also can resolve the difficulty to inspect substrate
internal defects after the substrate finished surface mount
process.
[0009] Therefore, it is the objective of the present invention to
provide a method for inspecting substrate internal defects for
receiving higher image definition of internal defects in a
substrate.
[0010] In order to achieve the above objective, the present
invention provides the method for inspecting substrate internal
defects, the substrate has an upper surface and a plurality of
lateral sides connected to the upper surface. The method for
inspecting substrate internal defects firstly provides at least one
light source disposed on one of the lateral sides on the substrate
and configured to emit a light beam to the lateral side for
correspondingly penetrating the substrate. The method also provides
an image capturing module disposed above the substrate for
retrieving an image of the upper surface, wherein an incident angle
of the light beam to the respective lateral side is limited within
a first predetermined angle to allow the light beam to have a total
reflection in the substrate.
[0011] Further, it is another objective of the present invention to
provide an apparatus for inspecting substrate internal defects for
receiving higher image definition of internal defects in a
substrate.
[0012] The present invention provides the apparatus for inspecting
substrate internal defects, wherein the substrate has an upper
surface and a plurality of lateral sides connected to the upper
surface. The apparatus for inspecting substrate internal defects
has at least one light source and an image capturing module. The
light source is disposed on one of the lateral sides on the
substrate and configured to emit a light beam to the lateral side
for correspondingly penetrating the substrate. The image capturing
module is disposed above the substrate for retrieving an image of
the upper surface, wherein an incident angle of the light beam to
the respective lateral side is limited within a first predetermined
angle to allow the light beam to have total reflection in the
substrate.
[0013] The present invention renders light beam transmitting into a
substrate and has a total reflection within the substrate where the
light beam does not refract out of the substrate. When light beam
is interfered by internal defects within the substrate, light beam
moving path is changed. Such changes of light moving path result in
reflection, refraction or scattering, and generate bright spots.
Thus, the defect locations are detected by an image capturing
module above the substrate. The method is effective in improving
image definition of internal defects and offering higher
detectability on internal defects
BRIEF DESCRIPTION OF DRAWING
[0014] The features of the invention believed to be novel are set
forth with particularity in the appended claims. The invention
itself, however, may be best understood by reference to the
following detailed description of the invention, which describes an
exemplary embodiment of the invention, taken in conjunction with
the accompanying drawings, in which:
[0015] FIG. 1 is a schematic diagram of an prior art apparatus for
inspecting substrate internal defects;
[0016] FIG. 2 is a schematic diagram illustrating the apparatus for
inspecting substrate internal defects performing a substrate
inspection;
[0017] FIG. 3 is another schematic diagram illustrating the
apparatus for inspecting substrate internal defects performing a
substrate inspection;
[0018] FIG. 4 is a schematic diagram of an apparatus for inspecting
substrate internal defects according to the present invention;
[0019] FIG. 5 is a schematic diagram of an apparatus for inspecting
substrate internal defects according to the present invention;
[0020] FIG. 6 is a schematic diagram of an apparatus for inspecting
substrate internal defects according to the present invention;
[0021] FIG. 7 is a curve diagram of light intensity to relative
image signal width and to relative image signal contrast ratio;
[0022] FIG. 8 is a schematic diagram of an apparatus for inspecting
substrate internal defects according to the present invention;
[0023] FIG. 9 is a schematic diagram of an apparatus for inspecting
substrate internal defects according to the present invention;
[0024] FIG. 10 is a schematic diagram of an apparatus for
inspecting substrate internal defects according to the present
invention; and
[0025] FIG. 11 is a schematic diagram from the other lateral side
of an apparatus for inspecting substrate internal defects according
to apparatus in FIG. 10.
DETAILED DESCRIPTION OF THE INVENTION
[0026] In cooperation with attached drawings, the technical
contents and detailed description of the present invention are
described thereinafter according to a preferable embodiment, being
not used to limit its executing scope. Any equivalent variation and
modification made according to appended claims is all covered by
the claims claimed by the present invention.
[0027] FIG. 4 is a schematic diagram of a preferred embodiment
according to the present invention. The apparatus for inspecting
substrate internal defects is suitable for use in internal defects
inspection of a substrate 40. The apparatus for inspecting
substrate internal defects mainly comprises a light source 50, and
an image capturing module 60.
[0028] The light source 50 is disposed on one of the lateral sides
43 of the substrate 40 to emit a light beam 51 to the lateral side
43 for correspondingly penetrating the substrate 40. Preferably,
the light beam emitted by the light source 50 is parallel light,
which means emitted light beam moves along the same path to have
stronger light beam transmitting in the substrate 40. In the
embodiment, the substrate 40 is a silicon wafer, the light source
50 selected is an infrared light source which is capable of
penetrating the silicon wafer accordingly. In other embodiments,
alternatives of the light source 50 are not limited to the above
embodiment. For example, if the substrate 40 is made of glass,
visible light source is applicable as the light source 50.
[0029] Substantially, as shown in FIG. 5, the substrate 40 of the
embodiment is a solar cell substrate, but is not limited to the
above in other embodiments. The substrate 40 has a main body 44, an
upper surface 41 and a lower surface 42, and a plurality of lateral
sides 43 connecting the upper surface 41 and the lower surface 42.
The upper surface 41 comprises a plurality of anti reflection
portion 411 and metal electrode portion 412 which are staggered,
wherein the anti reflection portion 411 is light transmissive and
the metal electrode portion 412 is light tight. The lower surface
42 is a light tight metal conducting portion. The plurality of
lateral sides 43 is largely perpendicular to the upper surface 41
and the lower surface 42.
[0030] It should be noted that, as shown in the FIG. 4, the
incident angle of the light beam 51 emitted by the light source 50
to the respective lateral side 43 is limited by a first
predetermined angle .theta.1 in order to effectively differentiate
substrate internal defects and external defects in the present
invention and assure the incident light beam 51 in substrate 40 has
a total reflection. The first predetermined angle .theta.1 is
determined according to wavelength of the light beam 51 and
refraction index of the substrate 40 and can be obtained by prior
art optical formulas.
[0031] In addition to limiting the incident angle of the light beam
51 within first predetermined angle .theta.1, because applied
thickness of the substrate 40 is mostly smaller than 1 mm and the
position of the substrate 40 relative to the position of the light
source 50 may offset slightly, the diameter of the light source 50
is usually larger than the thickness of the substrate 40 such that
emitted light beam by the light source 50 is allowed to transmit
into the substrate 40. Consequently, part of the light beam
transmitting onto the upper surface 41 of the substrate 40 may
scatter and become a part of the image taken by the image capturing
module 60. In order to avoid the scattering light effecting on the
contrast ratio of the image retrieved by the image capturing module
60, the incident angle of the light beam 51 according to the
present invention is further limited to the respective lateral side
43 within a second predetermined angle .theta.2. The second
predetermined angle .theta.2 is a far half the first predetermined
angle .theta.1 away from the image capturing module. The emitted
light beam 51 transmits to the substrate 40 by the second
predetermined angle .theta.2 instead of directly illuminating on
the upper surface 41, and transmits in the substrate 40 to have a
total reflection within the upper surface 41 or the lower surface
42 of the substrate 40 instead of refracting outside of the
substrate 40.
[0032] The image capturing module 60 is disposed above or beneath
the substrate 40 for retrieving images of the upper surface 41 of
the substrate 40. In the embodiment, the upper surface 41 of the
substrate 40 comprises the light transmissive anti reflection
portion 411 and the light tight metal electrode portion 412 and the
lower surface 42 is a light tight metal conducting portion. As a
result, the image capturing module 60 is disposed above the
substrate 40 for detecting reflection, refraction and scattering of
the light beam 51 generated by internal defects such as crack 45
and inclusion 46 via the anti reflection portion 412 of the upper
surface 41. The image capturing module 60 is not limited to some
specific models and can be any types of image detectors such as
cameras and recorders.
[0033] Generally speaking, when the light beam 51 illuminates on
the lateral side 43 of the substrate 40 with incident angle within
the second predetermined angle .theta.2, the light beam 51
transmits successfully in the substrate 40. If not, when incident
angle of the light beam 51 falls out of the second predetermined
angle .theta.2, only small part of the light beam transmits in
substrate 40 whilst most of the light beam penetrates the substrate
40 and generates a bright area, which may cause confusion when
interpreting the image data. Also, the ratio of the light beam
transmitting in the substrate 40 is lower as the light beam 51 has
larger offset from the second predetermined angle .theta.2.
[0034] Following the light beam 51 transmitting in the substrate
40, the majority of the light beam 51 has a total reflection within
substrate 40. Provided there is no defect in the materials of
substrate 40, then the light beam 51 does not refract out of the
substrate 40 and may continue to move until the energy exhausted or
transmit out of the substrate 40 from the other side of the lateral
sides 43. The light beam 51 can be interfered by the material
interface such as cracks 45 or internal defects resulting from
material difference such as inclusions 46, bubbles, internal
impurities when the light beam 51 transmits within the substrate
40. Under the circumstance, the moving path of the light beam 51
changes and light beam moving path is changed. Such changes of
light moving path result in reflection, refraction or scattering
transmitting outside of upper surface 41 of the substrate 40 to
generate bright spots. Thus, the defect locations are detected via
image capturing module 60 above the substrate 40. The photo of the
attachment 2 is a crack photo taken according to the present
invention. Compared to the photo of attachment 1 using prior art
defect inspecting method, the crack image of the present invention
is substantially more detailed.
[0035] However, foreign objects 47 on the upper surface 41 of the
substrate 40 almost have no effect on internal moving path of the
light beam 51 within the substrate 40. For example, foreign objects
47 on the upper surface 41 may include dusts, plastic particles,
oil stains, water marks and finger prints. Because light beam 51
from the substrate 40 does not penetrate foreign objects 47, the
photo retrieved by the image capturing module 60 does not include
the light beam 51 penetrating the location of the foreign objects
47. Therefore, the foreign objects 47 are not misidentified as the
internal defects of the substrate 40 in the image analysis.
Further, transmitted light beam through the micro surface texture
on the upper surface 41 of the substrate 40 caused by etching is
small that is not detectable by the image capturing module 60 so
that it is identified with the internal defects of the substrate 40
image capturing module.
[0036] FIG. 6 illustrates the method used by the present invention
is effective in improving image definition by increasing light
intensity to form signals of bright spots based on interface
scattering principles. The left part of the photo was taken with
lower light intensity. In contrast, the right part of the photo is
taken with higher light intensity. The higher light intensity
generates image signals of wider width of internal defects so that
the higher light intensity can be used for detecting extreme small
cracks on material interfaces. FIG. 7 is a curve diagram of light
intensity to relative image signal width and to relative image
signal contrast ratio. In FIG. 7, when the light intensity
increases, the image signal width of cracks increases and overall
contrast ratio decreases slightly which is beneficial to image
interpretation.
[0037] FIG. 8 is a schematic diagram of an apparatus for inspecting
substrate internal defects according to the present invention. The
embodiment further provide a plurality of light sources 50 to emit
light beam from multiple lateral sides 43, 43', 43'' of the
substrate 40 for penetrating the substrate 40 in order to further
increase image brightness and width of internal defects 49 in the
substrate 40. The plurality of light sources 50 can be linear light
source and parallel to the direction along the plurality of lateral
side 43, 43', and 43''. The internal defects 49 may be directional
as shown in the diagram. Under the circumstance, the extending
direction of the internal defects 49 is largely perpendicular to
the lateral side 43, the image brightness of the internal defects
generated by light beam from lateral side 43 is much lower than the
image brightness of the internal defects generated by light beam
from lateral side 43'. As shown in the FIG. 9, the image signal
width of the internal defects is effectively improved when light
beam transmits from multiple directions along the direction largely
perpendicular to the extending direction of the internal defects
49.
[0038] The problem that the amount of transmitted light beam is
small caused by directionality of the internal defects 49 can be
resolved by increasing brightness of the internal defects 49 via
transmit light beam from the lateral side 43, 43', 43'' of the
substrate 40. Since the image light intensity is superimposed by
light beam from multiple directions, image recognition rate on
micro cracks can be effectively improved, and required maximum
resolution of the image capturing module 60 can be lowered
significantly which offers advantages of lowering production cost
and providing more alternatives when choosing image capturing
modules.
[0039] FIG. 10 and FIG. 11 are other embodiments of the present
invention. Compared with the above embodiment, the embodiment
further comprises a carrier 70 for carrying the substrate 40, the
carrier 70 comprises a base 71 and a transmission module 72
disposed on the base 71. The transmission module 72 drives the
substrate 40 to move along a horizontal direction relative to the
image capturing module 60 (as the arrow direction shown in the FIG.
11). In addition, the light source 50 emits light beam towards the
lateral side 43 of the substrate 40 via a condensing lens 55 to
have the light beam focus on the lateral side 43. In other words,
the light beam emitted by the light source 50 illuminates only on
part of the lateral side 43 instead of illuminating on whole
lateral side 43. Further, the embodiment further uses a shading
plate 65 with an opening between the photo taking device 60 and the
substrate 40. The shading plate 65 is used for reducing the effect
of external light beam on the photo taking device 60 such that the
photo taking device 60 may precisely retrieve image of the upper
surface 41 of the substrate 40 through the opening on the shading
plate 65.
[0040] When the substrate 40 is driven by the transmission module
72 and moves along the horizontal direction relative to the photo
taking device 60, the light beam 51 emitted by the light source 50
scans horizontally on the lateral side 43 of the substrate 40 and
the photo taking device 60 take photos on the upper surface 41 of
the substrate 40 continuously. As such, the transmission module 72
continuously performs inspection on the substrate 40. Also, the
apparatus according to the embodiment can be integrated with on
line manufacturing process facilities to configure inspections pre
process, in process and post process.
[0041] As the skilled person will appreciate, various changes and
modifications can be made to the described embodiments. It is
intended to include all such variations, modifications and
equivalents which fall within the scope of the invention, as
defined in the accompanying claims.
* * * * *